Principal diagonal of the convolution array A213587.

Terms

a(0) =1a(1) =7a(2) =27a(3) =96a(4) =315a(5) =994a(6) =3043a(7) =9123a(8) =26909a(9) =78370a(10) =225911a(11) =645732a(12) =1832677a(13) =5170111a(14) =14509695a(15) =40537284a(16) =112805043a(17) =312808198a(18) =864707719a(19) =2383649115a(20) =6554153921a(21) =17980221382a(22) =49222822127a(23) =134495771976a(24) =366850762825